Optical communication systems may be used as high-bandwidth interconnects between electronic based processing systems. A signal is converted from the electrical realm to the optical realm on a transmitter side, launched into a transmissive medium (e.g., optical fiber), and then converted back to the electrical realm on a receiver side.
A number of photonic devices may be coupled with the transmissive medium between the transmitter side and the receiver side for manipulating the optical signal in a variety of manners, such as focusing, repeating/amplifying, routing, splitting, encoding/encrypting, and the like. Since propagation of an optical wave through a transmissive medium or photonic device is usually bi-directional (i.e., an optical wave can propagate in the forward and backward direction), these photonic devices can cause backward propagating reflections due to, for example, mismatches in an index of refraction at the interfaces of these photonic devices. If not blocked, these backward propagating reflections can disturb the operation of the optical communication system. A backward propagating reflection that enters the laser source on the transmitter side can interfere with stimulation emission within a resonance cavity of the laser source, and thereby cause unwanted noise limiting the performance of the optical communication system.
Optical isolators are often inserted inline between a laser source and a transmissive medium to block backward propagating reflections from entering the resonance cavity. Currently, optical isolators are standalone devices coupled to the output of an optical source via an optical fiber. Known standalone optical isolators include discrete, nonintegrated components such as a polarizer and a birefringent crystal rotator.